1. Field of the Invention
The present invention relates to a handy bottle provided with a pair of recessed portions for gripping and a process for producing same. More particularly, the present invention relates to a handy bottle featured firstly in that the periphery of the recessed portions for gripping on both sides (the wording “both sides” will be explained in detail hereinafter) are surrounded with a plane portion to absorb deviation in capacity of the contents caused by expansion or shrinkage of the bottle, and secondly in that the shortest distance between the deepest portion of the recessed portions for gripping on both sides is 50% or less of the diameter of the body portion while the shape in diametrical cross section of the recessed portions for gripping is approximately bilaterally symmetrical to a straight line passing through the body axis and the deepest portion.
The present invention relates also to a process for producing a handy bottle, which is featured by involving the steps of blow molding a bottle, while previously allowing movable inserts for molding the recessed portions for gripping to be on standby in a position at 2.0˜2.6 times ½ of the central diameter of a preform from the central axis of the preform, and allowing the movable inserts to proceed toward the deepest portion of the recessed portion for gripping in the course of the blow molding.
2. Description of the Prior Art
A bottle made of a synthetic resin provided with a recessed portion easy for griping, i.e. a handy bottle, finds it useful as a container for edible oils, condiments or seasonings of a relatively large volume. As the bottle is usually charged with the contents at a high temperature, an inner space of the bottle after cooling becomes more or less vacuum state. In case of a bottle provided with the recessed portions for gripping, it is naturally limited in the places where reduced pressure absorbing panel is provided, as compared with an ordinary bottle, so that deformation tends to take place in the body portion including a labeling portion. Thus, various countermeasures have been made to avoid such defect.
A handy bottle of this type has become handy by providing it with recessed portions for gripping to the body portion thereof, without using any separate foreign parts, in accordance with the request for saving cost and resource and for environmental problems. As the result, various countermeasures have been applied to avoid deterioration of strength. In such handy bottle, however, the so-called “buckling phenomenon” (a phenomenon of the recessed portions for gripping being pushed outward) tends to take place by impact at the time of dropping the bottle filled with the contents or by pressurizing the bottle at the time of checking any pinhole on manufacturing the bottle, so that too deep recessed portions for gripping cannot be molded. In case of a handy bottle devoid of such deep recessed portion, the bottle may still be easy for carrying but a considerable gripping power will be necessary instead. Thus, such handy bottle is not fully satisfactory in aspect of easiness for carrying and pouring the contents.
On consideration of the known conventional art, a technical idea of such handy bottle is known as shown in the accompanying FIGS. 19 and 20 wherein the notation a stands for a handy bottle, b for a shoulder panel, c for a back surface panel, and d for a bottom portion. In this case, any deforming power applied to the bottle is absorbed by the so-called panel effect of the panels provided in the shoulder, the back surface and the bottom portion to avoid deformation of a labeling portion.
This handy bottle a having a body portion f is circle in cross section and is inwardly recessed at the opposing two points of circle in cross section to form a vertically longer recessed portion g. A location of the two points where the bottle is inwardly recessed to form the recessed portions for gripping h is referred to herein as “both sides” of the bottle looking cylindrical in front view. The recessed portions for gripping g are provided with a plurality of reinforcing ribs h having protuberant top portions i, which extend across the recessed portion for gripping g. A gripping side (back side) of the bottle having a body portion c is provided with a plurality of reinforcing ribs j for preventing the buckling phenomenon.
As shown in the accompanying FIG. 21, a handy bottle a-1 is also known (Japanese Utility Model Publn. No. Hei. 4-20727), which has a body portion f provided on both sides thereof with opposing recessed portions c to form a gripping portion g. On the back side of the gripping portion g, a plurality of recessed reinforcing ribs h are formed which are orthogonally crossed with a central axis T of the bottle, and each of the ribs h forms a recessed portion i in the central portion thereof.
As another prior art, a handy bottle a-2 is known (Japanese Laid-open Patent Appln. No. Hei. 6-56138), which has a construction such that the bottle is recessed on both sides of a body portion f to form a pair of recessed portions for gripping c as shown in FIG. 22, and a reinforcing rib j in peripheral direction is formed from the lower part of the recessed portions for gripping c.
Also known is a bottle structure as shown in FIG. 23 wherein one side portion p of a handy bottle a-3 made of a synthetic resin where a label k is to be applied is made thicker in thickness while the other side portion m opposing to the side portion p is made thinner in thickness, the side portion m is provided with a reduced pressure-absorbing panel n capable of absorbing strain of the bottle a-3 under reduced pressure while the side portion m becomes protuberant from the side surface of the bottle a-3 to form a gripping portion o of a mountain shape in cross section and the back portion of this gripping portion acts as a reduced pressure-absorbing panel n (Japanese Utility Model Publn. No. Hei. 4-23766).
Further, a handy bottle as shown in FIG. 24 is known wherein a handy bottle a-4 having a body portion b is recessed inwardly from both sides of the body portion b to form a pair of opposing recessed portions for gripping c, a plurality of lateral ribs k are formed on the wall of a rear body portion between the pair of the recessed portion for gripping c while the recessed portion for gripping c is recessed inwardly by a rear slope l continuing from the end of the lateral rib k and a large curved surface continuing from the end of the lateral rib k to the wall of a front body portion n or recessed inwardly by a large curved surface continuing from the end of the lateral rib k to the wall of the front body portion m (Japanese Laid-open Patent Appln. No. Hei. 10-139028).
Such handy bottle is usually molded in such manner that a preform is inserted into a metal mold for blow molding which has been provided in opposing state with a pair of movable inserts capable of molding recessed portions for gripping, the preform is allowed to expand by stretching and blowing after heating the preform for softening, and when the volume becomes almost equal to 100% of the capacity of the metal mold, a pair of the movable inserts charged into the metal mold for blow molding are moved and pushed into the deepest position for forming the recessed portions for gripping thereby forming the recessed portions for gripping.
The handy bottle thus manufactured becomes thicker in thickness in the deepest portion of the recessed portion for gripping while becoming thinner in both side portions, thus making a tendency of unbalance in lateral direction. Moreover, the bottom portion becomes thicker and a heal portion just above the bottom portion becomes thinner, thus making a tendency of unbalance in vertical direction.
Consequently, the so-called buckling phenomenon takes place by impact at the time of dropping the bottle or by pressuring the bottle at the time of checking any pinhole so that too deep recessed portions for gripping cannot be molded. Even in case of a handy bottle devoid of such deep recessed portions for gripping, the bottle may still be easy for carrying but a considerable gripping power will be necessary instead. Thus, such handy bottle cannot be said to be fully satisfactory.
In consideration of such problems raised in the manufacture of handy bottles, a method for manufacturing handy bottles, which prevents the tendency of becoming thinner in both side portions, is known (Japanese Laid-open Patent Appln. No. Hei. 2-72925). According to this method, a preform is expanded by stretching or blowing after it is heated and softened whereby its volume reaches to at least 80% but not more than 100% of the capacity of a metal mold for blow molding, and at this moment a pair of movable inserts mounted to the metal mold are allowed to proceed and pushed into the deepest portion where the recessed portions for gripping is formed thereby forming the recessed portion to prevent a tendency of making both side portions thinner.